Lighting up marine organisms
Animals that are experiencing physical damage or early signs of stress can be visually identified using excitation light that induces fluorescence.
There is an increasing need for methods that can accurately measure stress in aquaculture species, without harming the organism. Hyperspectral imaging of biofluorescence is such a method, as it can potentially measure early signs of stress in both fish and invertebrates.
The fish and invertebrates that exhibit biofluorescence emit lower energy colored light when they are exposed to higher-energy blue light. This strong fluorescence is not visible to the naked eye, but it can be measured with hyperspectral imaging.
“Fish may exhibit welfare traits in ways that are invisible to the human eye, and one of our objectives is to explore new technologies that can reveal this to us in real-time”, says Evan Durland, scientist in aquaculture genetics and project leader.
Welfare indicators are important because animals that experience chronic stress are vulnerable to disease, experience less growth, and ultimately have a higher mortality rate. The current methods used to identify early signs of stress in marine species have certain limitations.
Glowing when stressed
Technology scientists Samuel Ortega and visiting PhD student Thomas Juhasz investigated the applications of using hyperspectral imaging of biofluorescence as a welfare indicator for marine species, particularly lumpfish, red king crab, and green sea urchins.
The scientists found that lumpfish and red king crabs produced stronger fluorescent emissions after exposure to stressors. Put in simple words, the animals glowed more brightly when they experienced acute stress. They also found that sea urchins with broken spines or lesions glow brighter in the areas where they are affected.
The scientist has ideas for how to improve the technology:
“We want to see if we can integrate artificial intelligence (AI) into this method. The AI can analyze the biofluorescence data acquired through hyperspectral imaging, and alert us if it detects any fluorescence changes that may indicate stress in the animals. We believe that this could contribute significantly to the future of welfare measurement during aquaculture operations”, says Samuel Ortega.
The research was funded by the EU Horizon 2020 program through the AquaVitae project, and by Nofima through the Deep Vision project. The research was done by Nofima in collaboration with Marie Curie PhD student Thomas Juhasz in 2022.
Scientific publications
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Biofluorescent response in lumpfish Cyclopterus lumpus to a therapeutic stressor as assessed by hyperspectral imaging
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Environmental challenge trials induce a biofluorescent response in the green sea urchin Strongylocentrotus droebachiensis
Stress in sea urchins leads to high mortality and economic losses in both the environment and aquaculture. The green sea urchin Strongylocentrotus droebachiensis has been documented emitting complex biofluorescence, yet how this responds to external stressors is unknown. Adult sea urchins (n = 210) were divided between control (n = 30) and experimental groups (n = 180), using three transport variables: out of water, in water at elevated temperatures, (warm-water) and in water at seawater temperature (cold-water). Hyperspectral imaging of external fluorescence and fluorospectrometric analysis on coelomic fluid was measured at five intervals (hour 0,3,6,9,12). External green emissions (∼580 nm) responded to all treatments, peaking at h9. External red emissions (∼680–730 nm) in the cold-water remained low until an h9 peak. The warm water increased emissions at each interval, peaking at h9. The out of water gradually increased, with the highest at h12. The coelomic fluid fluorescence (∼680 nm) was low to nonexistent except in warm-water, whose elevated levels suggest that fluorescent emissions are a measurable byproduct of internal adaptation(s) to stress. Early detection of fluorescent emissions (broken spines, lesions) may prevent economic losses. The observed link between fluorescence and the applied stressors provides a baseline for developing non-invasive technology for improving echinoderm welfare.
Stress in sea urchins leads to high mortality and economic losses in both the environment and aquaculture. The green sea urchin Strongylocentrotus droebachiensis has been documented emitting complex biofluorescence, yet how this responds to external stressors is unknown. Adult sea urchins (n = 210) were divided between control (n = 30) and experimental groups (n = 180), using three transport variables: out of water, in water at elevated temperatures, (warm-water) and in water at seawater temperature (cold-water). Hyperspectral imaging of external fluorescence and fluorospectrometric analysis on coelomic fluid was measured at five intervals (hour 0,3,6,9,12). External green emissions (∼580 nm) responded to all treatments, peaking at h9. External red emissions (∼680–730 nm) in the cold-water remained low until an h9 peak. The warm water increased emissions at each interval, peaking at h9. The out of water gradually increased, with the highest at h12. The coelomic fluid fluorescence (∼680 nm) was low to nonexistent except in warm-water, whose elevated levels suggest that fluorescent emissions are a measurable byproduct of internal adaptation(s) to stress. Early detection of fluorescent emissions (broken spines, lesions) may prevent economic losses. The observed link between fluorescence and the applied stressors provides a baseline for developing non-invasive technology for improving echinoderm welfare.
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